Lab 12: Dissolved Oxygen and Aquatic Primary Productivity

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  1. Why is there less oxygen at higher temp?
    air is less dense
  2. What is primary productivity?
    the rate at which organic materials are stored
  3. How can you measure PP?
    • rate of CO2 utilization
    • rate of O2 formation
    • rate of formation of organic compounds
  4. A measure of oxygen production provides what?
    a means of calculating the amt of carbon that has been bound in organic compounds over a period of time
  5. the change over time in DO concentration from the initial concentrations is a measure of __.
    net productivity
  6. The differnece over time between the DO concentrations in the light bottle and hte dark bottle is the total oxygen production and therefore an estimate of __.
  7. How do you find...
    • NPP= (Light- Initial)
    • GPP= (Light - Dark)
    • Respiration= (Initial - Dark)
  8. How do you find the oxygen saturation?
    You get the Oxygen mg and the water temp and connect the two. So in the middle there should be a point that crosses the % saturation line
  9. For the graph what is the independent variable and what is the dependent variable?
    • inde: % of light
    • dep: gross productivitiy
  10. How should you do the graph?
    • on the x-axis there should be increasing % of light, starting with 0
    • on the y- axis, increasing GPP (DO concentration in ppm)
  11. What are three ways primary productivity can be measured?
    • rate of CO2 utilization
    • rate of formation of organic compounds
    • rate of O2 production
  12. What is the relationshipp between oxygen production and assimilation of carbon?
    • The measure of O2 production gives us a means of measuring te amount of carbon bound in organic compounds;
    • for each milliliter of oxygen produced, .536 milligrams of carbon has been assimilated.
  13. From your graph, what is the effect of temp on the amt of oxygen that water at differnet temps can hold?
    the colder the temp, the more dissolved oxygen is present (for every liter of water, there is 5-10 ml of DO) At warmer temps, there is less present
  14. Why does a mammal use only 1-2% of its energy in ventilation but a fish uses 15% of energy?
    • this is the case because there is an abundance of Oxygen in the air, so we dont have to compete or expend energy trying to get it
    • fish live in water, where DO is limited. Therefore, due to the little amt and comp for it, they must expend a considerable amt of energy to get it. (5-10 ml/ 1 L water)
  15. Would DO in water taken from a stream entering a lake to be higher or lower tan DO from a lake?
    higher becuase the agitation facilitates oxygen diffusion; also there may be less animals in the water that will compete for DO
  16. WOuld you expect the DO concentration of water samples taken from a lake at 7 AM to be higher or lower than samples taken at 5 PM?
    • Lower because at 5 PM the water has been exposed to sunlight over the course of the day so DO levels increased due to photosynthesis occurring;
    • - However, it may also be higher because more PP could elevate DO during hte course of the day. However, at 7 the sun is just beginning to come out so it is likely that it is lower because it was dark before that
  17. In a drawing with fish in identical containers with differnet volumes of water, which would have the most oxygen available?
    B because there is less water, so there is more access to the sunlight. Also, a larger surface area is good in gas exchange. Gas exchange is dependent on surface area.
  18. What is eutrophication?
    the process by which nutrients (P or N) become highly concentrated in a body of water and cause a mass production of algae and cyanobacteria
  19. Why is allowing N or P fertilizers to run into a body of water have a negative affect life.
    Although it increases DO production due to the massive algae that can carry out photosynthesis, when they die they cause a massive deadzone. Also, the algae when they die, take up all the oxygen, making it unavailable to other organisms.
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Lab 12: Dissolved Oxygen and Aquatic Primary Productivity

AP Bio
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